The present disclosure relates, in general, to a system for controlling ignition timing in an internal combustion engine. Even more particularly, the present disclosure relates to an ignition system having a microcontroller and a programmer for changing values stored in the microcontroller.
In high performance combustion engine applications, such as drag racing, a capacitive discharge ignition system is often preferred because a capacitive discharge ignition system is fast and efficient at providing energy for creating sparks, especially at high speeds. A capacitive discharge ignition system uses a storage, or xe2x80x9cbathtub,xe2x80x9d capacitor to hold energy until the correct time to make the spark. The capacitor is connected to an ignition coil of the engine through a switch such that, to generate a spark, the switch is activated to dump the charge from the capacitor to a primary side of the ignition coil in less than {fraction (1/10)}th of a millionth of a second. The charge from the capacitor is then stepped up by the turns ratio of the ignition coil and applied to spark plugs of the engine for igniting fuel within combustion chambers of the engine.
The capacitor can be charged extremely fast and can hold energy for extended periods, with almost no loss or leakage, and then can release the energy to the ignition coil very quickly. Thus, a capacitive discharge ignition system provides an extremely fast and efficient method of storing and distributing energy to create sparks in an engine, with no drop off in engine performance at high speeds.
However, the quicker, hotter sparks of a capacitive discharge ignition system results in a shorter duration for each spark, which can disrupt engine performance at low speeds. At high engine speeds, a shorter duration spark is not a problem since the spark is supposed to occur very quickly. But at low engine speeds, the shorter duration sparks can result in poor performance because cylinder pressures and temperatures are low and air/fudel mixtures can be less than optimal. Thus, it is preferable that a capacitive discharge ignition system automatically provide multiple sparking, or xe2x80x9crestrikes,xe2x80x9d at low engine speeds to ensure excellent engine performance.
A capacitive discharge engine will preferably also include an engine speed, or rev, limiter feature to protect the engine from dangerous high speeds, or xe2x80x9cover-revving,xe2x80x9d wherein the engine could be damaged or even explode. A rev limiter feature turns off the spark to individual cylinders of the engine when engine speed exceeds a preset maximun level. Thus, the engine is purposely caused to misfire so that the engine speed is brought back down to the preset maximum level.
In addition a digital ignition system is preferable to an analog ignition system since a digital ignition system is generally not effected by temperature and humidity and, thus, provides more accurate and consistent engine performance. A digital ignition system utilizes a microcontroller, which includes a central processing unit and memory, for controlling system functions such as restrikes, rev limiters, engine speed activated switches, spark duration, and ignition timing. Because a microcontroller is not effected by temperature and humidity, like the resistors of an analog system, a digital ignition system utilizing a microcontroller is simply more accurate and consistent and, therefore, preferred. A digital system also provides greater flexibility and convenience.
Furthermore, all features of an ignition system, such as restrikes, rev limiters, engine speed activated switches, spark timing retards and timing curves, will preferably be provided in an integrated package such that add-on boxes and other additional components are not necessary and do not have to be added to the ignition system once installed in a vehicle.
Most importantly, a preferred ignition system will include means for instantaneously, and remotely, programming system function values. By instantaneously and remotely, it is meant that the ignition system should allow a user to be seated in a driver""s compartment of a vehicle incorporating the ignition system, while the vehicle is positioned at a starting line at the beginning of a race, with the engine either running or turned off, to instantaneously change system settings.
Accordingly, what is still needed is a digital capacitive discharge ignition system that provides numerous features such as multiple sparks and over rev protection, wherein all features are provided in a fully integrated package, and wherein the ignition system includes means for instantaneously and remotely programming system function values.
The present diclosure, therefore, provides an ignition system for energizing an ignition coil of an internal combustion engine. The system including a high voltage unit for energizing the ignition coil of the engine, a memory for storing system function indices and a processor. The processor receives a timing signal from an engine speed pick-up device, accesses the memory to retrieve the system function indices, and causes the high voltage unit to energize the ignition coil based on the system function indices and the frequency of the timing signal. The system also includes a programmer in communication with the processor for allowing a user to instruct the processor to select and modify the system function indices during engine operation.
Another ignition system for energizing an ignition coil of an internal combustion engine is also disclosed. The system includes a high voltage unit for energizing the ignition coil of the engine, a memory for storing a system function index, and a processor. The processor receives a timing signal from an engine speed pick-up device, accesses the memory to retrieve the system function index, and causes the high voltage unit to energize the ignition coil based on the system function index and the frequency of the timing signal. The system also includes an input device having a microcontroller for converting user inputs into a value for the system function index, communicating the value to the processor, and instructing the processor to insert the value into the system function index.
A process for changing values stored in function indices within an ignition system microcontroller in response to user inputs through a remote programmer having function, value and scroll switches and a display is also disclosed. The function indices are accessed by the ignition system to calculate ignition timing. The process includes monitoring the function and the value switches of the programmer, displaying a function code if the function switch is selected, displaying a different function code if the scroll switch is selected, displaying a value for a last displayed function code if the value switch is selected, and displaying a different value for the last displayed function code if the scroll switch is selected. The process also includes saving a last displayed value of the last displayed function code into a random access memory of the microcontroller. The last displayed value of the last displayed function code is then saved in a system function index corresponding to the last displayed function code if the function switch is selected. The system function index is located within programmable read-only memory of the microprocessor accessed by the ignition system to calculate ignition timing.
Another process for changing values stored in function indices within an ignition system microcontroller in response to user inputs through an input device having a switch and first and second indicators is disclosed. The function indices are accessed by the ignition system to calculate ignition timing. The process includes scanning the switch, accessing an index of a random access memory to retrieve an old value of the switch stored in the index of the random access memory, comparing a scanned value of the switch to the old value of the switch, turning on the first indicator if the scanned value and the old value are not equal, and causing the scanned value to be stored in the system function index of the programmable read only memory. The process also includes replacing the old value with the scanned value of the switch in the index of the random access memory, and turning on the second indicator and turning off the first indicator.
Still other features and advantages will become apparent upon reading the following detailed description in conjunction with the drawings and the appended claims.